1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copier, a printer, a facsimile machine or a multifunctional apparatus that provides the function of each of these apparatuses, and relates particularly to a power-saving technology, for an image forming apparatus, that performs a pre-heating function in a stand-by state.
2. Description of the Related Art
An improvement in image quality, an increase in printing speed and a reduction in the time required for the first recording material to be output are features generally sought in image forming apparatuses, such as electrophotographic printers, copiers and facsimile machines. Further, on the market, added values, such as extension for optional functions and a power-saving method, are now in greater demand than previously. And especially, with regards to a power-saving method, an internationally recognized power-saving program, such as the Energy Star or the Blue Angel, is adapted for electric apparatuses. Furthermore, during the production of image forming apparatuses, environmental problems are actively taken into consideration.
An image forming apparatus includes a toner fixing device, which applies heat to melt the toner in an unfixed toner image, formed on a recording sheet or an OHP sheet, to fuse the toner to the sheet and to produce a permanent, fixed image.
Of the various types of image forming apparatuses available, there are some for which fixing devices should be warmed up (pre-heated) while such apparatuses are on printing stand-by. These types include, for example, full color printers, wherein rubber layers are formed on fixing devices used to fix toner images, and fast printers, which produce a large number of prints per unit time. Since the fixing device of such an apparatus has a large heat capacity, the fixing device is warmed up during the printing stand-by state of the image forming apparatus, thereby reducing the period required to output a recording material bearing a toner image.
The most effective power-saving method for an image forming apparatus is one that reduces the power consumed during the printing stand-by state of the image forming apparatus. Normally, printing is seldom performed continuously, throughout a day, and during a day, the image forming apparatus normally remains in the stand-by state rather longer than in the printing state. Therefore, reducing the power consumed during the stand-by state is the most effective method by which to reduce cumulative power consumption (effectively reduces the cumulative power consumption [W·h]: Watt Hours). Generally, the electric power required to pre-heat a fixing device (electric power consumed per unit time) accounts for 90% or greater of the total power consumed by a printer in the stand-by state (power consumed per unit time). Therefore, when the power consumed by the fixing device during each printing stand-by period is effectively reduced, the overall affect produced is a reduction in the cumulative power consumed.
On the other hand, power savings can be provided by simply not performing the pre-heating of the fixing device during stand-by periods, and the economic merit afforded by the power thus saved will accrue to a user. However, the warm-up period required to reach a fixing temperature would be extended, and usability would deteriorate.
Therefore, according to one proposal, provided in Japanese Patent Application Laid-Open No. H05-323710, a user can set a transition period from the end of printing to the power-saving mode. Currently, however, a demand exists for an improved system.